Apparatus for uniform vaporisation of high melting materials in particular quartz



mmmmm @mmuan mawzazw Jan. 6, 170 K. DIETZEL 1,488.42

APPARATUS FOR UNIFORM VAPORISATION OF HIGH MELTING MATERIALS INPARTICULAR QUARTZ Filed Apri]; 24, 1967 "INVENTOR.

KARL D/ETZEL ATTO/Q NE/VJ United States Patent 09 Int. Cl. Hb 1/00,7/00; B23k 9/00 US. CI. 13-31 4 Claims ABSTRACT OF THE DISCLOSUREControl elements in the primary winding of the special high voltagesupply unit to maintain constant output power from the power supply forthe operation of electron guns used to, vaporize quartz for depositionin the vaporized phase upon synthetic resin surfaces including anapparatus to maintain the quartz or inorganicmaterial surface to bevaporized in the same position in relation to the focus of electronbeams from the electron gun and to continuously keep the angle ofvaporization constant by the rotating movement of the inorganic orquartz material, a rate at which the material is consumed forvaporization.

The invention relates to an apparatus for the uniform vaporisation andapplication of high melting materials, in particular quartz in a highvacuum to synthetic resin surface in which is provided a source emittinga beam of electrons, and. having magnetic focussing, a support for thematerial which is vaporised at the focal pointof the electron beam, anda high voltage supply apparatus to produce the electron beam.

Such apparatuses are used for vapour phase deposition of coatings onarticles for surface finishing. Toobtain a uniform coating and compactadherence, it is absolutely essential "for the material to be vaporisedcompletely uniformlyg;

In known appagatuses, a power supply unit supplying direct voltage, asas possible free from ripple voltages, is used for the source ofelectrons for producing the electron beam. The disadvantage of such asupply unit is that when quartz is vaporised, dissociation takes place,owing to excessively high local temperatures obtained in the quartz byexcessively sharp focusing. The rate of vaporisation also depends to amajor extent on the body which is being vaporised. The body usually usedhas hitherto been located at the focal point of the electron beam andinto which a furrow was burnt. As a result, there was a constant changein the angle of vaporisation which in the ideal case should be 180 inorder to ensure uniform rate of vaporisation. This resulted in anonuniform layer of deposited vapour being obtained, which layer wassubject to powerful mechanical stresses and had poor adhesion andinsufiicient hardness. These disadvantages can only be avoided if careis taken to ensure that the rate of vaporisation is kept as constant aspossible throughout the vaporisation time by keeping the temperature atthe focus and the vaporisation angle of 180 unchanged.

According to the invention, this is achieved by arranging automaticallyand continuously operating cont'rol members such as thyristors,transducers or electron tubes, into the primary winding of the highvoltage supply unit in order to maintain at a constant value the outputvoltage required for vaporisation, and by inserting the material to bevaporised into a rotatable and at ICE the same time axially displaceablesupport which con-- voltage that is rich in ripple voltages since thismeasure,

surprisingly, has a particularly advantageous effect on focussing andhence vaporisation. The voltage peaks in the high voltage causeimmediate recommencement of vaporisation if, during one half wave, thecurrent has exceeded the permissible level due to excessive vapourpressure, and in the next, following half wave the output has beendiminished by the cut in control-by means of the continuously operatingoutput control member. In the half wave following this cut in controlthe peak, which is rich in ripple voltages occurs owing to the cut incontrol and again caiises recommencem'ent of vaporisation of the quartz,which acts as insulator. Since this entire process takes place within 3to 4 half waves, the quartz is unable to cool during this brief time, incontrast to the phenomena which have been observed with the power supplyunits hitherto used. This results in a completely uniform rate ofvaporisation.

The body which is to be vaporised is preferably cylindrical and isadvantageously kept vertical with its upper end surface permanentlysituated at the focal point by means of the feed device constantlymoving the body forwards in a spiral movement. According to theinvention, the focus is so adjusted that [the diameter of the focus isequal to ,;the radius of the body being vaporised and extendsunilaterally from the centre of the end surface to the edge of thatsurface. This shape and arrangement of the body' to be vaporised ensure,together with the control members of the power supply unit, very uniformvaporisation and an angle of v orisation which can always be kept atapproximately 190.

The invention will now be described diagrammatically with reference tothe accompanying drawing.

The phases R, S, T"of a power supply unit lead to control members which;are in the form of transducers 1, the transmittance of which iscontrolled by an auxiliary transformer 2. The transducers 1 areconnected to a transformer 3 which has a voltage of,,,for example, 380volts at the input end but 10 kv. at the hight voltage end, with whichan earthed rectifier 4 is connected in series. A smoothing resistor 5and smoothing condenser 6 serves to filter off part of the high-ripplevoltage. The main component of the source of electrons is a cathode 9,the heating of which is controlled by an auxiliary transformer 7 via atransformer 8. The source of electrons further comprises an earthedplate 10, an insulator 11 which is constructed as a support, a shield12, a focus sing cup 13 and an auxiliary anode 14. A permanent magnet 15with magnetic yoke 16 deflects and focuses the electron beam 17 obtainedinsuch a'manner on to a quartz rod 18 which is to be vaporised, andwhich serves as anode so that the focus extends from the centre of thequartz rod 18 to a point on the edge of the rod. The quartz rod 18 ismounted in an externally screw threaded support 19 which is continuouslymoved upwards in a screw threaded tube 20 by a drive 21 at a ratecorresponding to the rate of vaporisation.

I claim:

1. In combination with an apparatus and three-wire, three-phase powersource of the type wherein a high voltage supply unit, means foremitting a beam of electrons, means for focussing the beam of electrons,and means for positioning an object at the focal point of the beam ofelectrons are provided for uniform vaporization of high meltingtemperature materials in a high in the highly electrically conductivestate of vapori zed material by means of controlling impedance forincreasing and decreasing potential to the high voltage supply unit;

means for applying a large potential with minimal cuit current whendirect current potential momentarily decreases, thereby re-institutingthe electron beam after direct current discontinuance because ofshortcircuited interruption drawing down direct current potential belowfiring potential level; and

device for simultaneously rotating and axially displacing the materialto be vaporized onto the synthetic resin material, said device disposedto hold one surface of the material to be vaporized in the same planecontaining the focal point of the applied electron beam, and the axiallydisplaceable rate of travel for maintaining this position beingdependent on the amount of vaporized material and the vaporization rate,thereby the angle of vaporization is kept constant at approximately 180degrees as -the material is vaporized.

Apparatus as claimed in claim 1, wherein said cirfor impedance controlcomprises:

transformer with primary windings connected between two of the phases ofthe three-wire, threephase circuit conductors, so that the same voltageis coupled to said isolation transformer secondary windings, forelectrically isolating the power source;

a variable-position autotransformer with primary windings connected inparallel with secondary windings of said isolation transformer, so thatthe same voltage is applied to the primary windings of saidvariable-position autotransformer, for stepping-down voltage andstepping-up current applied to the primary windings of saidautotransformer; fixed-position autotransformer, with primary windingsconnected in parallel with the secondary windings of said isolationtransformer so that the same voltage is applied to the primary windingsof said fixed-position autotransformer, for stepping down voltage andstepping-up current applied to the primary windings of saidautotransformer; and cathode-heater transformer with primary windingsconnected in parallel with the secondary winding portion of primarywindings of said variable position autotransformer so that the samevoltage is applied to said cathode-heater transformer, saidcathode-heater transformer secondary winding being center-tap connectedto the direct current potential output of the high voltage supply unit,superimposing thereon an alternating-current potential output of saidvariable-position autotransformer for supplying power to the electronbeam emitting means, the alternating current potential output portionbeing used to heat the cathode, wherein by a sudden electrical dischargethe voltage decreases towards zero until the electron beam isinterrupted whereupon the means for controlling impedance reduces thepotential drop to the high voltage supply unit allowing maximumpotential to be developed for application to the electron beam emittermeans within one cycle permitting vaporization and deposition to beuniform. Apparatus as claimed in claim 1, wherein said impedance controlmeans comprises:

at least one transducer connected between one phase output of thethree-wire, three phase-power source and one input to the high voltagesupply unit for increasing or decreasing the resistance in the conductorfor providing greater or lesser power feedback control;

a transformer with primary windings connected be tween two of the phasesof the three-wire, threephase circuit conductors so that the samevoltage is coupled to said isolation transformer secondary windings forelectrically isolating-the-power source;

a fixed-position autotransformer, with primary windings connected inparallel with the secondary windings of said isolation transformer sothat the same voltage is applied to the primary windings of saidfixed-position autotransformer, for stepping down voltage andstepping-up current applied to the primary windings of saidautotransformer;

a second transformer, with primary windings connected in parallel to thesecondary winding portion of the primary windings of said fixed positionautotransformerso that the same voltage is applied to the primarywindings of said transformer, said transformer coupledelectromagnetically to said transducer; and

means for rectifying the alternating-current output of said transformerand applying the direct current to said transducer for increasing ordecreasing the flux reluctance in said transducer, the change of fluxreluctance resulting during a half cycle of the sinusoidal input of onephase of the three-phase input to the high voltage supply unit wherebythe change in flux reluctance causes a change in power control in theone phase conductor to the high voltage supply unit.

4. In combination with an apparatus and three-wire, three-phase powersource of the type having a high voltage supply unit for producing ahigh direct current potential, means of emitting a beam of electrons,means of focusing the electron beam and support means for holdingmaterial at the focal point of the electron beam for uniformvaporization and application of high melting temperature materials in ahigh vacuum onto synthetic resin material'surfaces, wherein theimprovement comprises:

a transformer with primary windings connected between two .of the phasesof the three-wire, threephase circuit conductors so that the samevoltage is coupled to said isolation transformer secondary windings forelectrically isolating the power source from interference by anysubsequent circuitry;

a h red position autotransformer, with primary windings connected inparallel with the secondary windings of said isolation transformer sothat the same voltage is applied to the primary windings of saidflied-position autotransformer, for stepping-down voltage andstepping-up current applied to the primary windings of saidautotransformer;

three transducers inserted between each phase of the three-phase powersource and the high voltage supply unit having three input connections,one for each of; the three-wire, three-phase conductors;

three transformers, with primary windings of each connected in parallelto the other and to the second winding portion of the primary windingsof said fixed-position autotransformer so that the same voltage isapplied to the primary windings of said three transformers, one each ofsaid three transformers coupled electromagnetically into saidtransducers;

means for rectifying the alternating current output of said threetransformers and applying the resulting direct current through saidtransducers thereby controlling the impedance presented by saidtransducers between the three-phase power source and high voltage supplyunit during one-half cycle;

a variable-position autotransformer, with primary windings connected inparallel with secondary windings of said isolation transformer so thatthe same voltage is applied to the primary windings of saidvariable-position autotransformer, for stepping-down voltage andstepping-up current applied to the pri; mary windings of saidautotransformer; and

5 6 a cathode-heater transformer with primary windings contion anddeposition of high melting temperature nected in parallel with thesecondary winding portion materials takes place.

of primary windings of said variable-position autotransformer so thatthe same voltage is applied to said References Cited cathode-heatertransformer secondary windings being 5 UNITED STATES PATENTS centertapconnected to the direct-current output of 2,994,801 8/1961 Hanks X thehigh voltage supply unit superimposing thereon 3268648 8/1966 Dietrich 29 121 X an alternating-current output of said variable-posi- 3 27 902 1019 Ab 219 121 X tion autotransformer for supplying current to the3,277,865 10/1966 simi h 13 31 X electron beam emitting means withregard to several 10 3,300,561 1/ 1967 Four,

break downs in a few seconds of the electron beam 3,303,320 2/1967Muller 219-121 by electrical discharges in the vacuum during -evap-3,328,672 6/1967 Park 13--31 oration, the breakdown and immediatelyfollowing 3,347,701 10/ 1967 Yamagishi et a1 219-421 X reignition, willcause an output with a maximum 15 peak voltage five to ten times greaterthan the mean BERNARD GILHEANY, Pmnary Examiner voltage level, wherebythe electron beam emitting GILSQN, Assistant Examiner means isconstantly and continuously refired within 1 one cycle after shortingduring the vaporization state U.S. Cl. X.R

when the material is electrically conductive, reduc- 20 ing reignitiontime to within one cycle as vaporiza-

